1. Field of the Invention
The present invention generally relates to weapons and artillery and, more particularly, to penetrating type weapons that may be used, for example, to detect media layers in an effort to locate and destroy sheltered targets.
2. State of the Art
In military operations, targets may be generally classified as either unsheltered targets or sheltered targets. Unsheltered targets may be considered to include targets that are substantially exposed and vulnerable to a weapon or projectile fired by artillery directed at such targets. For example, people, munitions, buildings and other fighting equipment that are openly located on a battle field and substantially exposed to the weapons of an enemy attack may be considered unsheltered targets.
However, many targets including, for example, people, munitions, chemicals, and fighting equipment may be sheltered in order to protect them from an attack by various weapons. Conventionally, a shelter for a target includes a physical barrier placed between the target and the location of origin of an expected enemy weapon in an attempt to frustrate the weapon directed at the target and mitigate the damage that might otherwise be inflicted by such a weapon. In some cases targets may be heavily sheltered in an attempt to prevent any damage to a given target. In one example, one or more layers of concrete, rock, soil, or other solid material may be used in an effort to protect a desired target. Each layer may be several feet thick, depending on the level of protection desired. Sometimes these layers are referred to as “hard” layers indicating a relative amount of resistance that they will impose on an impending weapon. Generally, a layer is considered to be “hard” when it exhibits a specified level of thickness, when it is formed of a material exhibiting a specified level of hardness or some other material characteristic which significantly impedes penetration of a weapon, or when the layer exhibits a desired combination of material properties and physical thickness.
More specific examples of shelters for targets include a building, a room in a building, a bunker, a room in a bunker, or a room or a bunker located beneath a building. Considering a bunker as an example, the ceiling of a bunker may be configured as a hard layer in order to protect people, things, or a combination thereof, from non-penetrating weapons. Additionally, multiple hard layers may be used to shelter a target. Voids may be present between multiple layers for structural reasons or for purposes of trying to confuse existing weaponry designed to defeat such shelters by causing premature detonation.
In order to penetrate shelters, and particularly a hard layer (or layers) of a given shelter, a weapon system configured with a penetrator system is conventionally used. The general goal of using a penetrator system is to breach the shelter, including any thick layers that may be present, and deliver the weapon to a desired location (i.e., proximate the intended target) while delaying detonation of the weapon until it is at the desired location. Thus, use of a penetrator system enables a more efficient and a more effective infliction of damage to a sheltered target and, sometimes, use of a such a system is the only way of inflicting damage to certain sheltered targets.
A penetrator system is part of a weapon system which may include one or more warheads, a penetrator structure (generally referred to as a penetrator) and a sensor associated with and coupled to the penetrator. The penetrator may be configured to act as a warhead, or it may be a separate component, but generally includes a mass of relatively dense material. In general, the capability of a penetrator to penetrate a given layer of media is proportional to its sectional density, meaning its weight divided by its cross-sectional area taken along a plane substantially transverse to its intended direction of travel. The weapon system may include equipment for guiding the weapon to a target or, at least to the shelter, since, in many cases, forces associated with impact and penetration of a shelter may result in the removal of such equipment from the penetrator portion of the weapon. The sensor of a penetrator system is conventionally configured to assist in tracking the location of the penetrator as it penetrates layers of one media type or another after an initial impact of the penetrator with the shelter.
Various prior art penetrator systems have been employed with some degree of success. In some prior art penetrator systems, a sensor is used to detect an initial impact with a structure. The system then monitors the amount of time that has lapsed subsequent the detected impact in an effort to keep track of the location of a penetrator, based on calculated or estimated velocity of the weapon, as the penetrator penetrates a shelter. Such systems are sometimes referred to as time-delay systems.
Other prior art penetrator systems utilize sensors, such as an accelerometer, to measure the deceleration of the penetrator. The system then tracks the distance traveled by the weapon, from the time of the initial impact with a layer of a shelter or structure, in an effort to determine the weapon's location within the shelter or structure. These systems are generally referred to as penetration depth systems.
Some prior art penetrator systems utilize an accelerometer to detect deceleration of relatively hard and/or thick layers in an effort to help count the layers of media, count voids between the layers of media, or count both media layers and voids so as to determine the weapon's location within a particular structure.
Such prior art penetrator systems provide an output signal for detonating the weapon after the penetrator system has determined that the penetrating weapon has arrived at a desired location within the shelter. Desirably, the detonation of the weapon occurs at a target site such as within a specified room of a bunker. However, in practice, any of a number of factors may result in the miscalculation of a penetrating weapon's location within a shelter and, therefore, detonation of the weapon at an undesired location. Such factors may include, for example, variability in the physical or material characteristics of a given layer.
One particular issue faced by prior art penetrator systems includes the ability to detect so-called thin layers. While penetrator systems have been used to detect decelerations that result from the presence of a relatively thick or hard layer, such penetrator systems have not been effective in accurately detecting layers that are thin, soft, or some combination thereof, due to the relatively low amount of deceleration experienced by the penetrating weapon when passing through such thin or soft layers. Some examples of “thin” layers include ceilings and floors in buildings that may be located over a target. Some examples of “soft” layers include layers of sand or other soft soil. Generally, a layer is too thin or too soft to detect when the deceleration of a penetrating weapon, as it passes through such a layer, cannot be discerned from electrical noise, mechanical noise, or a combination of electrical and mechanical noise experienced by the sensor.
Some prior art systems have utilized gain switching in an effort to detect relatively thin layers. Gain switching generally includes use of a high gain amplifier to detect low levels of deceleration by the penetrating weapon and use of a lower gain amplifier as deceleration of the penetrating weapon increases. Such gain switching may occur between a computer sampling of the penetrating weapon's deceleration. Gain switching may generally be accomplished using one or more amplifiers, one or more analog-to-digital converters, or some combination thereof.
Nevertheless, such systems have not been effective in detecting layers that are as thin as those exhibited in numerous targets such as the thin roofs and floors of many buildings. Reducing noise in a sensor can help to increase the sensitivity of penetrator systems employing gain switching; however, reducing noise still does not provide the level of sensitivity needed to ensure that all layers, regardless of how thin, are detected.
Some prior art penetrating systems have actually attempted to avoid detection of thin layers so that the attendant errors in detecting soft or thin layers do not confuse the system and result in the untimely detonation of the penetrating weapon. For example, some attempts have been made to adjust the sensor thresholds of a penetrator system so that they only detect so-called “hard” layers and effectively ignore all thin or soft layers of a shelter. However, such attempts unfortunately result in the sensor ignoring a layer that is significant to a well-timed detonation such as, for example, the ceiling of a bunker, again resulting in the detonation of the penetrating weapon at an undesired location.
In other prior art penetrator systems, attempts have been made to not only ignore thin layers, but to prevent the system from erroneously counting a single layer as more than one layer. To do so, such penetrator systems have used a programmed distance, sometimes referred to as a “blanking distance,” to ignore both false layers and real layers after the penetrator system has detected a deceleration of the weapon. In one example, a prior art penetrator system would calculate and measure the blanking distance traveled by the penetrator system based on the penetration velocity of the penetrator system at the time of its impact with a layer and the time that expired after such impact. Some other penetrator systems have also used the deceleration values and the detection of an exit of the penetrating weapon from a penetrated layer to help determine the blanking distance.
However, accurate detection and recognition of soft and thin layers is desirable in many applications, and simply ignoring such layers does not ensure detonation of the penetrating weapon at the desired location. As such, there is a continued desire to improve the penetrator systems used in weapons so as to increase their accuracy in determining their arrival at a desired location, including the detection of soft or thin layers, and thereby ensure a maximization of damage inflicted on a desired target. It would be desirable to provide such improvements through simple implementations so, for example, existing prior art systems may be updated and retrofitted in a simple and inexpensive manner.